This invention relates to a recording head which ejects ink from ejection nozzles and performs image recording on a recording medium. The present invention also relates to an inkjet recording apparatus including such recording head.
As the above-described inkjet apparatus, inkjet recording apparatus having a function, wherein air entered an ink supply path, connecting an ink tank and ejection nozzles, is removed, have been conventionally known. Especially among such inkjet recording apparatus, there are inkjet apparatus including an ink supply path, wherein a sectional area of the upper portion of the path is larger than that of the lower portion. In this kind of inkjet recording apparatus, the flow speed of ink in the upper portion of the ink supply path is relatively low, and air (air bubbles) do not easily move from the upper portion of the path to the lower portion.
Generally, in an inkjet recording apparatus, an ink supply path, connecting an ink tank and ejection nozzles, is provided with a pressure chamber and a restriction part. The pressure inside of the pressure chamber becomes high due to a piezoelectric element. The restriction part inhibits ink from reversely flowing toward the ink tank. That is, the sectional area of the restriction part is configured to be smaller than that of the pressure chamber. Because of this restriction part, the resistance generated when ink flows becomes large, and the reverse flow of ink is inhibited.
In the above-described conventional inkjet recording apparatus, the configuration is devised in the ink supply path from the restriction part toward the side of the ink tank. Therefore, when air enters the restriction part, an air removal process is required in order to remove the air.
In a recent inkjet recording apparatus, an ink supply path is disposed in a bent manner in order to make the size of the entire apparatus small. In such inkjet recording apparatus, air is easily accumulated in the bent portion. In order to remove the accumulated air, ink in the bent portion needs to be moved at relatively high speed.
As a result, there has been a problem that a large amount of ink is wasted so as to remove air inside of an ink supply path.
In consideration of the above and other problems, in a recording head and an inkjet recording apparatus, air accumulated in the ink supply path is preferably removed merely by discharging as small amount of ink as possible.